Inflammatory bowel disease (IBD) is a common name for the diseases of unknown cause represented by ulcerative colitis and Crohn's disease where chronic inflammation and/or ulcer are/is induced in the large and small intestinal mucosa. Many of the patients develop the disease in relatively young age between teens to twenties showing clinical symptoms such as diarrhea, fever or abdominal pain or systemic inflammatory symptoms and it has been a problem that not only nutrition of food/beverage orally ingested is unable to be efficiently absorbed but also social life is deteriorated due to dietary restrictions and frequent evacuations. As to the cause for the inflammatory bowel diseases, abnormal autoimmune and enterobacteria have been reported but the cause has not been clarified yet and it is the current status that no therapeutic means resulting in complete cure has been found yet.
As to the treatment for inflammatory bowel diseases such as ulcerative colitis, a drug therapy using salazosulfapyridine, 5-aminosalicylic acid, steroids or immunosuppressants or a dietary therapy has been carried out already. However, no sufficient therapeutic effect is achieved by that and, moreover, in steroids and immunosuppressants, side effects due to a long-term administration are becoming a big problem.
On the other hand, the present heterocyclic derivative (1) or a pharmaceutically acceptable salt thereof has already been reported to be useful for the treatment of pulmonary hypertension or obstructive arteriosclerosis as a PGI2 receptor agonist (see, for example, Patent Document 1).
Patent Document 1: Pamphlet of International Publication WO 02/088084